One common way to extend the battery life of a portable device is to reduce the LCD backlight intensity. In contrast to previous approaches that minimize the power consumption by adjusting the backlight intensity frame by frame to reach a specified image quality, the proposed method optimizes the image quality for a given backlight intensity. Image is enhanced by performing brightness compensation and local contrast enhancement. For brightness compensation, global image statistics and backlight level are considered to maintain the overall brightness of the image. For contrast enhancement, the local contrast property of human visual system (HVS) is exploited to enhance the local image details. In addition, a brightness prediction scheme is proposed to speed up the algorithm for display of video sequences. Experimental results are presented to show the performance of the algorithm.